Process of detinning aluminum



Jan. 12, 1932. w. FRA NKEL' 1 ,s40,70s

PROCESS OF DETINNING ALUMINUM Filed Jan. 14, 1930 Maw- ' aftoz u qo.

Patented Jan. 12, 1932 WALTER FRAENKEL, F FRALl'KFORT-ON-THE-MAIN, GERMANY, ASBIGNOR TO AMERICAN LU'RGI CORPORATION, OF NEW YORK, N.

YORK

Y., A GORPORATION.OF NEW PROCESS OF DETINNING ALUMINUM Application filed January 14, 1930, Serial No. 420,749, and in Germany March 20, 1929.

The ob'ect of the present invention is a process 0 detinning aluminum.

It is known that aluminum is not miscible or is only slightly miscible with a number of metals, such as for example lead, cadmium, bismuth, sodium, potassium and thallium 1n the liquid state, whereas tin forms completely miscible alloys with said metals in the liqu d state.

If stanniferous aluminum is treated with such metals, and afterwards caused to deposit in the liquid state or if it is caused to solidify, the tin disperses in the two phases and in different ratios according to the various metals used.

When stanniferous aluminum is treated with lead for example, the partition coefficient of tin between the two phases is approximately unity, so that when employing equal weights of both aluminum and lead, approximately one half of the tin remains in the aluminum and the other half enters the lead. It is therefore generally not possible to remove the whole of the tin from aluminum in one operation. By repeating the process however,

the aluminummay be detinned to any desired extent.

The tin which is present in the non-alumi-- num phase, can be recovered therefrom acao cording to known methods. Moreover the tin lead alloy thus produced for example may be employed without further treatment.

I have found that a considerable improve-' .ment of the process can be effected if instead of employing the detinning metal (such as lead) in the pure state, a substanceis added thereto, which is adapted to forma compound with the tin. Such substances are for example the alkali metals such as sodium. An addition 40 of this character effects a considerable increase of the partition coefficient in many cases. For example, when employln a lead- I sodium'alloy-containing 10% of so ium the- 5 said"coefficient is increased to'about 3, with the result that thetin may be removed very his as follows considerably from the aluminum with the use of this alloy with fewer repetitions of the process.

In order to avoid the necessity of always employing fresh quantities of detinning metal, according to a further feature of the invention the purifying of the aluminum can be combined with that-of the detinning metal and moreover at the same time and in one and the same vessel.

To this end, according to the invention, an arrangement of the plant is employed as shown, for example in the drawing.

In the drawing 1 depicts an electrolyzing vessel. 2 is the molten detinning metal, in m the present case lead, with which the stanniferous aluminum layer 4 communicates by means of a tube 3 openat the bottom. A molten layer of lead chloride 5 is arranged outside the tube 3 upon the layer of lead 2. 05 A cathode 6 dips into the lead layer 2, whilst anode 7 dips into the lead chloride layer. 8 is a tube for-leading oif volatile products.

The process is carried out in this appara- The tin of the stanniferous aluminum 4 distributes itself according to the partition coefficient between the aluminum and the lead on the one hand and between the lead s and the lead chloride on the other hand un- 76 til a state of equilibrium is reached which is represented in the lattercase by the equation:

Sn+PbGl s P +snon This equilibrium continuously disturbed by 80 electrolysis and by the removal of the tin as stannic chloride, which is distilled ofl from the lead chloride phase through the tube 8,

with the result that fresh quantities of tin The process may be carried out either'continually or also in batches. 7

Claim A process of separating tin from a mixture containing aluminum and tin which comprises treating the said mixture in a molten condition with a metal of the group consisting of lead, cadmium and bismuthto which an alkali metal has been added.

In testimony whereof I afix m%signature.

WALTER ,FRA NKEL. 

